This invention relates to a cold cathode electronic device, and a field emission luminous device and a cold cathode luminous device each including such a cold cathode electronic device. More particularly, the present invention relates to a cold cathode electronic device which includes a cathode electrode, a gate electrode and an anode electrode and is constructed so as to permit electrons field-emitted from the cathode electrode to reach to at least one of the gate electrode and anode electrode, and a field-emission luminous device and a cold cathode luminous device each including such a cold cathode electronic device, wherein cold cathode is improved in emission characteristics and a phosphor is stabilized in luminous efficiency.
When an electric field set to be about 109 (V/m) is applied to a surface of a metal material or that of a semiconductor material, a tunnel effect occurs to permit electrons to pass through a barrier, resulting in the electrons being discharged to a vacuum even at a normal temperature. Such a phenomenon is referred to as xe2x80x9cfield emissionxe2x80x9d and a cathode constructed so as to emit electrons based on such a principle is referred to as xe2x80x9cfield emission cathode (FEC)xe2x80x9d.
Recently, development of semiconductor fine-processing techniques permits a field emission cathode of the surface emission type to be constructed of field emission cathode elements having a size as small as microns. Various electronic units wherein a number of field-emission cathodes are arranged in a matrix-like manner on a substrate each function to impinge electrons selectively emitted from emitters on a phosphor, to thereby permit the phosphor to selectively emit light, resulting in being used as an electron feed means for a flat-type display device.
Now, such a conventional field emission display (FED) will be described with reference to FIG. 12. The field emission display is called a Spindt-type display device.
An FEC of the Spindt type includes a first substrate or cathode substrate 100, which is then formed thereon with a cathode electrode 101. The cathode electrode 101 is then formed thereon with a resistive layer 102, an insulating layer 103 and a gate electrode 104 in order in an upward direction. The gate electrode 104 and insulating layer 103 are formed with holes in common to each other in a manner to extend therethrough, in each of which an emitter electrode 115 of a conical shape in vertical section is provided while being placed on the resistive layer 102. The emitter electrodes 115 each are arranged in the hole while being exposed at an acute distal thereof through the hole.
Use of fine processing techniques for manufacturing of such an FEC permits a distance between the conical emitters 115 and the gate electrode 104 to be reduced to a level lower than a micron, so that mere application of a voltage as low as about tens of volts permits the emitter electrodes 115 to emit electrodes as desired.
Above the first substrate 100 on which a number of such FECs are arranged in an array is provided a second substrate or an anode substrate 116 constituting an anode electrode in a manner to be opposite thereto. The first substrate 100 and second substrate 116 cooperate with each other, as well as a side plate to form an airtight envelope, which is evacuated to form a vacuum or reduced pressure therein, resulting in the FED being provided.
In the FED thus constructed, a gate voltage Vg is applied between the gate electrode and the cathode electrode and an anode voltage VA is applied between the cathode electrode and the anode electrode, so that electrons emitted from the emitter electrodes 115 may be impinged on a required portion of the phosphor on the anode substrate 116, resulting in desired luminous display being provided.
FIG. 13 shows a drive unit for driving a color FED in which such an FEC of the surface emission type as described above is incorporated. The FED designated at reference numeral 151 in FIG. 13 is constructed into an FED panel structure having mxc3x97n dots. Reference numeral 152 designates an image signal (image data) inputted, 153 is a signal input buffer, and 154 is a controller for generally controlling the whole panel.
The controller 154 functions to permit the image data inputted thereto through the signal input buffer 153 to be temporarily stored in a display RAM 155, for example, for each of the three primary colors red, green and blue (RGB) in each frame unit. Also, the controller 154 acts to transfer the thus-stored RGB image data to data drivers (cathode drivers) 156A and 156B depending on a display system.
The data drivers 156A and 156B output, to cathode terminals Cl to Cm, a cathode voltage Vcc inputted thereto from a cathode power supply 160B of a power supply 160 and a data pulse subjected to pulse modulation depending on a gradation of the RGB image data from the controller 154.
In this instance, the power supply 160, as described above, includes the cathode power supply 160B for applying the cathode voltage Vcc to the data drivers 156A and 156B, as well as a gate power supply 160A for applying a gate voltage Vgg of a predetermined level to a gate voltage control circuit 159.
Reference numeral 158 designates an anode power supply/anode switch circuit 158, which functions to apply an anode voltage of a predetermined level to anode terminals A1 and A2 of the FED panel 151 according to control 154 by the controller.
The gate voltage control circuit 159 has an operation order of gate terminals G1, G2, . . . of the FED panel 151 and timings thereof set therein and functions to feed a pulse voltage of a predetermined level to a scan driver (gate driver) 157 depending on the gate voltage Vgg from the gate power supply 160A.
The scan driver 157 is fed with a scan signal for scanning each of the gate terminals G1, G2, . . . of the FED panel 151 from the gate voltage control circuit 159 according to control by the controller 154. The scan driver 157 functions to drive each of picture cells arranged on the matrix according to a so-called linear sequential system for sequentially selecting the gate terminals G1, G2, . . . , depending on a display system.
In FIG. 13, cathode data of the data drivers 156A and 156B and a voltage level of the gate drive signal from the gate voltage control circuit 159 are appropriately set depending on the cathode voltage Vcc outputted from the power supply 160, so that a dynamic range of luminance in a display section may be adjusted.
As described above, the conventional field emission display (FED) is so constructed that the field emission cathode and the anode conductor provided thereon with the phosphor layer are arranged opposite to each other in the airtight envelope.
More specifically, in manufacturing of the conventional FED, the cathode conductor is formed on an inner surface of the cathode substrate constituting a part of the airtight envelope and then the insulating layer is formed on the cathode conductor, followed by formation of the gate on the insulating layer. Then, the holes are formed through the gate and insulating layer and then the emitter electrodes each are formed in each of the holes while being arranged on the cathode conductor, resulting in the FEC being provided. The anode arranged opposite to the FEC thus provided is provided by forming the light-permeable anode conductor on an inner surface of the anode substrate constituting another part of the airtight envelope and then forming the phosphor layer on the anode conductor.
In the FED thus constructed, a voltage of a suitable level is applied to each of the gate and anode conductor while applying a voltage of a predetermined level to the cathode, to thereby permit electrons to be emitted from a distal end of the emitter electrodes. Then, the electrons thus emitted impinge on a desired portion of the phosphor layer of the anode, leading to luminescence of the phosphor, which is externally observed through the anode conductor and anode substrate.
Unfortunately, the conventional FED constructed as described above causes the emitter electrodes to be polluted during mounting of the FEC structure in the airtight envelope, resulting in an emission threshold level of the emitter electrodes being increased, leading to a reduction in emission characteristics thereof or a deterioration in long-term reliability of luminous efficiency of the phosphor.
This would be due to the fact that the emitter electrodes and the phosphor layer of the anode electrode are oxidized by O2 or polluted with C or the like adhered thereto. Such oxidation or pollution is increased with a lapse of operation time. For example, with regard to an affection of the oxidation or contamination to emission performance of the emitter electrodes, an anode current is caused to be rapidly reduced due to the affection as shown in FIG. 14, resulting in luminance characteristics of the phosphor layer being rapidly deteriorated.
In view of the foregoing, the assignee proposed techniques of cleaning emitter electrodes by irradiation of electron beams during manufacturing of an FED, as disclosed in Japanese Patent No. 2,634,295. The techniques proposed are constructed so as to impinge a part of electrons emitted from emitter electrodes on non-emitting emitter electrodes which are kept from emitting electrons, leading to cleaning thereof.
For this purpose, the emitter electrodes are electrically classified into a plurality of pairs of emitter electrode groups. When the emitter electrodes of one of the groups in each pair is under the normal conditions of emitting electrons, a positive potential of a level equal to or higher than that of a gate of the emitter electrodes of the one group is applied to the emitter electrodes of the other group. Such drive conditions are alternately changed over for every emitter electrode groups in each pair. This permits a part of electrons emitted from the emitter electrodes of one of the groups in each pair to impinge on the emitter electrodes of the other group to clean them. Similarly, electrons emitted from the emitter electrodes of the other group impinge on the emitter electrodes of the one group, to thereby clean them.
However, the techniques of cleaning the emitter electrodes by irradiation of emitted electrons thereon fail to satisfactorily ensure emission characteristics of the FED having a narrow gap and luminous efficiency of the phosphor layer.
Also, driving of the emitter electrodes while dividing them into a plurality of groups not only requires to electrically divide the cathode conductor for the emitter electrodes, but requires individual drive circuits.
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide a cold cathode electronic device which is capable of removing pollution of emitter electrodes during manufacturing of the device, to thereby prevent a deterioration in emission characteristics of the emitter electrodes, as well as a deterioration in luminous efficiency of a phosphor layer.
It is an object of the present invention to provide a field emission luminous device which is capable of removing pollution of emitter electrodes during manufacturing of the device, to thereby prevent a deterioration in emission characteristics of the emitter electrodes and a deterioration in luminous efficiency of a phosphor layer.
It is a further object of the present invention to provide a cold cathode luminous device which is capable of removing pollution of emitter electrodes during manufacturing of the device, to thereby prevent a deterioration in emission characteristics of the emitter electrodes and a deterioration in luminous efficiency of a phosphor layer.
In order to attain the above-described objects, the present invention is so constructed that hydrogen occlusion metal is included in at least a part of at least any one of a gate electrode and an anode electrode and a part of electrons field-emitted is impinged on the hydrogen occlusion metal to activate it, to thereby permit the hydrogen occlusion metal to discharge hydrogen. The hydrogen thus discharged functions to prevent pollution of emitter electrodes and a phosphor layer.
The hydrogen occlusion metal referred to herein means metal or alloy which cooperates with hydrogen to form a hydrogenated material. The hydrogen is stored between crystal lattices of the metal. The amount of hydrogen stored is known to be hundreds of times as volume as the metal. Elements for a matrix of the hydrogen occlusion metal include Nb, Zr, V, Fe, Ta, Ni, Ti, Mg, Th or a combination thereof.
Thus, in the present invention, for example, supposing that the emitter electrode or phosphor layer has O2 gas and C adhered to a surface thereof, hydrogen gas discharged from the hydrogen occlusion metal effectively removes O2 gas and C, because it reacts with the O2 gas and C to form OH and CH, respectively. Also, the residue gas reacts directly with hydrogen, resulting in O2 gas an C adhered being effectively reduced.
In accordance with one aspect of the present invention, a cold cathode electronic device is provided. The cold cathode electronic device includes a cathode electrode for field-emitting electrons, a gate electrode, and an anode electrode. The electrons field-emitted from the cathode electrode are permitted to reach at least any one of the gate electrode and anode electrode at the time when a gate voltage is applied between the gate electrode and the cathode electrode and an anode voltage is applied between the cathode electrode and the anode electrode. At least a part of at least any one of the gate electrode and anode electrode includes hydrogen occlusion metal.
Also, in accordance with this aspect of the present invention, a cold cathode electronic device is provided. The cold cathode electronic device includes a cathode electrode for field emitting electrons, a gate electrode, and an anode electrode. The electrons field-emitted from the cathode electrode are permitted to reach at least any one of the gate electrode and anode electrode at the time when a gate voltage is applied between the gate electrode and the cathode electrode and an anode voltage is applied between the cathode electrode and the anode electrode. At least a part of at least any one of the gate electrode and anode electrode includes hydrogen occlusion metal. The cold cathode electronic device also includes a control unit for varying a drive signal fed to any electrode selected from the cathode electrode, gate electrode and anode electrode. The drive signal varied by the control unit permits the amount of electrons emitted to be controlled by controlling a current of any electrode selected from the gate electrode and anode electrode, so that the electrons controlled are impinged on the hydrogen occlusion metal to discharge hydrogen gas therefrom.
In a preferred embodiment of the present invention, the drive signal fed to any electrode selected from the cathode electrode, gate electrode and anode electrode is a pulse signal, wherein a variation of the pulse signal is a variation in any one selected from the group consisting of a pulse width of the pulse signal, a pulse height thereof and the number of pulses thereof.
In a preferred embodiment of the present invention, the pulse signal is varied in correspondence to a variation in an anode current of the anode electrode detected.
In a preferred embodiment of the present invention, when the anode current is reduced, a current of the electrode of which at least a part includes the hydrogen occlusion metal is increased to increase discharge of hydrogen gas from the hydrogen occlusion metal, to thereby enhance electron emission of the cathode electrode; and when the anode current is increased, a current of the electrode of which at least a part includes the hydrogen occlusion metal is reduced to reduce discharge of hydrogen gas from the hydrogen occlusion metal, to thereby stabilize electron emission of the cathode electrode.
In a preferred embodiment of the present invention, the hydrogen occlusion metal is selected from the group consisting of Nb, Zr, V, Fe, Ta, Ni and Ti.
In a preferred embodiment of the present invention, the hydrogen occlusion metal occludes CH4 gas as well as the hydrogen gas and discharges CH4 gas as well as the hydrogen gas due to impingement of the electrons thereon.
In accordance with another aspect of the present invention, a field emission luminous device is provided. The field emission luminous device includes a cathode electrode including emitter electrodes for field-emitting electrons, a gate electrode, and an anode electrode including a phosphor layer for emitting light due to impingement of the electrons thereon. The electrons field-emitted from the cathode electrode are permitted to impinge on the anode electrode, leading to luminescence of the phosphor layer. At least a part of the gate electrode includes hydrogen occlusion metal. The anode electrode is applied thereto a voltage lower than an electron drawing voltage applied to the gate electrode at the time of luminescence of the phosphor layer under the conditions that a voltage is kept applied to the anode electrode or the gate electrode is applied thereto an electron drawing voltage while a voltage is kept from being applied to the anode electrode in response to switching of the anode electrode. The hydrogen occlusion metal has the field-emitted electrons impinged thereon during non-luminescence of the phosphor layer, resulting in hydrogen gas being discharged from the hydrogen occlusion metal.
In accordance with this aspect of the present invention, a field emission luminous device is provided. The field emission luminous device includes a cathode electrode including emitter electrodes for field-emitting electrons, a gate electrode, and an anode electrode including a phosphor layer for emitting light due to impingement of the electrons thereon. The electrons field-emitted from the cathode electrode are permitted to impinge on the anode electrode, leading to luminescence of the phosphor layer. The anode electrode includes a display anode electrode including the phosphor layer and a hydrogen discharge anode electrode which is electrically separated from the display anode electrode and free of the phosphor layer and of which at least a part includes hydrogen occlusion metal. The hydrogen discharge anode electrode is fed with a drive signal independent from that of the display anode electrode. The hydrogen occlusion metal of the hydrogen discharge anode electrode has the field-emitted electrons impinged thereon, to thereby discharge hydrogen gas therefrom.
Further, in accordance with this aspect of the present invention, a field emission luminous device is provided. The field emission luminous device includes a cathode electrode including emitter electrodes for field-emitting electrons, a gate electrode, and an anode electrode including a phosphor layer for emitting light due to impingement of the electrons thereon. The electrons field-emitted from the cathode electrode are permitted to impinge on the anode electrode, leading to luminescence of the phosphor layer. At least a part of the gate electrode includes hydrogen occlusion metal. The field emission luminous device also includes a focusing electrode arranged between the gate electrode and the anode electrode and has a voltage applied thereto. The voltage applied to the focusing electrode is controlled to vary a rate of distribution of a current fed to the gate electrode and anode electrode, so that a required amount of electrons may be impinged on the hydrogen occlusion metal of the gate electrode to discharge a required amount of hydrogen gas from the hydrogen occlusion metal.
In accordance with a further aspect of the present invention, a cold cathode luminous device is provided. The cold cathode luminous device includes a cathode conductor, a cold cathode arranged on the cathode conductor so as to emit electrons, an anode conductor, and a phosphor layer arranged on the anode conductor. The electrons emitted from the cold cathode are impinged on the phosphor layer, leading to luminescence of the phosphor layer. The phosphor layer has a hydrogen occlusion metal powder added thereto.
In a preferred embodiment of the present invention, the hydrogen occlusion metal powder is adhered to a surface of the phosphor layer or a surface of a phosphor particle constituting the phosphor layer.
In a preferred embodiment of the present invention, the phosphor layer is formed of a paste made by mixing a phosphor particle and the hydrogen occlusion metal powder with each other.
In a preferred embodiment of the present invention, the phosphor layer is constituted of a phosphor powder of 1 to 10 xcexcm in particle size and the hydrogen occlusion metal powder has a particle size of 0.01 to several xcexcm.
Moreover, in accordance with this aspect of the present invention, a cold cathode luminous device is provided. The cold cathode luminous device includes a cold cathode conductor for field-emitting electrons, an anode conductor, a phosphor layer arranged on the anode conductor so as to emit light due to impingement of the electrons thereon, and an airtight envelope in which the cold cathode, anode conductor and phosphor layer are received. The envelope has hydrogen gas encapsulated therein. The phosphor layer has a hydrogen occlusion metal powder added thereto.